Triangle RST was transformed using the rule (x, y) → (–x, –y). The vertices of the triangles are shown.R (1, 1)S (3, 1)T (1, 6) R' (–1, –1)S' (–3, –1)T' (–1, –6)

The rule (x, y) → (−x, −y) changes the sign of both coordinates. A 180° rotation about the origin sends each point to the point directly opposite it, which follows this rule: for example, R(1, 1) becomes R′(−1, −1). So the transformation was a 180° rotation about the origin.

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